Facial Nerve Disorders

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Facial Nerve Disorders

Otology/Audiology
Author Credentials 

Jeffrey T. Vrabec, MD
Professor
Department of Otolaryngology Head and Neck Surgery
Baylor College of Medicine
Houston, TX

Module Summary

The pathophysiology of facial nerve dysfunction is highly variable. A careful history and physical examination is essential for proper diagnosis. Intervention may be directed toward preservation or improvement of function in acute lesions, while chronic lesions require efforts to minimize deformity and restore movement.   

Module Learning Objectives 
  1. Develop a differential diagnosis for facial nerve dysfunction based on a thorough history and physical examination. 
  2. Recognize the most common causes of acute facial palsy and provide effective evidence based intervention. 
  3. Appropriately order and interpret imaging and electrical testing to characterize prognosis. 
  4. Discuss utility and limitations of available medical and surgical therapies. 

Embryology

Learning Objectives 

Recognize developmental facial nerve disorders.  

  • Hemifacial Microsomia  
  • Mobius syndrome: Bilateral facial nerve and abducens nerve agenesis   
  • Facial nerve hypoplasia is frequently associated with Aural Atresia in CHARGE, Goldenhar (OAVS oculoauricular vertebral spectrum)
References 
  1. Sataloff RT. Embryology and Anomalies of the Facial Nerve and their Surgical Implications.  New York: Raven Press; 1991.
  2. May M, Schaitkin B. The Facial Nerve. New York: Thieme; 2000.
  3. Terzis JK, Anesti K. Developmental facial paralysis: a review. J Plast Reconstr Aesthet Surg. 2011;64:1318-33.

Anatomy

Learning Objectives 
  1. Understand sensory and motor functions of the facial nerve. 
    • Nervus intermedius is comprised of special sensory afferents (Taste), general sensory afferents (sensation of the concha and posterior ear canal), and visceral motor efferents for lacrimation salivation, and nasal mucus secretion.
  2. Discuss the course of the facial nerve from the brainstem, through the temporal bone to the facial musculature. 
  3. Identify the clinical symptoms of facial nerve dysfunction and the significance in localizing the site of lesion.  
References 
  1. Gulya AJ, Minor LB, Poe D eds. Glasscock-Shambaugh Surgery of the Ear. 6th ed. Shelton CT: Peoples Medical Publishing; 2010.  
  2. Slattery WH, Azizzadeh B. The Facial Nerve. New York: Thieme; 2014.

Pathogenesis

Learning Objectives 

Discuss prevailing theories of pathogenesis for common facial nerve disorders.  

  • Viral reactivation accounts for most cases of acute facial palsy after excluding trauma, neoplasms, intracranial infections, stroke, and iatrogenic causes.   
  • Bell palsy is due to reactivation of Herpes simplex virus (HSV).
  • Ramsay Hunt syndrome is due to reactivation of varicella zoster virus (VZV).
References 
  1. Murakami S, Mizobuchi M, Nakashiro Y, Doi T, Hato N, Yanagihara N. Bell palsy and herpes simplex virus: identification of viral DNA in endoneurial fluid and muscle. Ann Intern Med. 1996 Jan 1;124(1 Pt 1):27-30.
  2. Slattery WH, Azizzadeh B. The Facial Nerve. New York: Thieme; 2014.

Basic Science

Learning Objectives 

Understand physiology of nerve injury and regeneration.

References 
  1. Sunderland S. Nerves and nerve injuries. 2nd ed. New York: Churchill Livingstone; 1978. 

Incidence

Learning Objectives 

Discuss incidence of facial nerve disorders.

  • Acute facial palsies from viral mediated inflammation 
    • Bell Palsy (~ 20/100000 persons annually)
    • Ramsay Hunt  (~ 2/100000 persons annually)  
  • Trauma
    • Facial nerve injury is most likely with fractures involving the otic capsule.
    • Penetrating facial trauma has greater probability of facial nerve transection. 
References 
  1. Campbell KE, Brundage JF. Effects of climate, latitude, and season on the incidence of Bell's palsy in the US Armed Forces, October 1997 to September 1999. Am J Epidemiol. 2002;156:32-9.
  2. Katusic SK, Beard CM, Wiederholt WC, Bergstralh EJ, Kurland LT. Incidence, clinical features, and prognosis in Bell's palsy, Rochester, Minnesota, 1968-1982. Ann Neurol. 1986;20:622-7.
  3. Yanagihara N. Incidence of Bell's palsy. Ann Otol Rhinol Laryngol Suppl. 1988;(137):3-4.
  4. Sweeney CJ, Gilden DH. Ramsay Hunt syndrome. J Neurol Neurosurg Psychiatry.  2001 Aug;71(2):149-54. 
  5. Brodie HA, Thompson TC. Management of complications from 820 temporal bone fractures. Am J Otol. 1997;18:188-97.

Patient Evaluation

Learning Objectives 
  1. Understand the importance of history in developing differential diagnosis.  
    • Acute onset of dysfunction is seen with trauma, infectious and inflammatory disease, and stroke.
    • Progressive dysfunction is seen in benign and malignant neoplasms and neurodegenerative disease.
  2. Presenting symptoms will vary depending on the site of nerve involvement.
    • Central disorders exhibit other signs of neurological dysfunction.
    • Auditory and vestibular symptoms may result from disorders affecting the intratemporal and intracranial segments of the nerve. 
    • Segmental dysfunction is seen in pathology distal to the pes anserinius.  
References 
  1. May M, Schaitkin B. The Facial Nerve. New York: Thieme; 2000.
  2. Slattery WH, Azizzadeh B. The Facial Nerve. New York: Thieme; 2014.
  3. Niparko JK. The acute facial palsies. In: Jackler RK, Brackmann DE, editors. Neurotology: principles and practice. St Louis, MO: Mosby; 1994.

Measurement of Functional Status

Learning Objectives 

Discuss methods for evaluating and measuring facial nerve dysfunction.

  • Validated measuring scales provide ease of use and high interobserver agreement for communicating facial nerve function.
  • Evoked EMG or electroneuronography (ENoG) can predict the severity of nerve injury when evaluated 4-14 days after the onset of complete paralysis. 
  • Electromyography is most useful more than 3 weeks after the onset to detect reinnervation. 
References 
  1. House JW, Brackmann DE. Facial nerve grading system. Otolaryngol Head Neck Surg. 1985;93:146-47.
  2. Ross BG, Fradet G, Nedzelski JM. Development of a sensitive clinical facial grading system. Otolaryngol Head Neck Surg. 1996 Mar;114(3):380-6.
  3. Vrabec JT, Backous DD, Djalilian HR, Gidley PW, Leonetti JP, Marzo SJ,Morrison D, Ng M, Ramsey MJ, Schaitkin BM, Smouha E, Toh EH, Wax MK, Williamson RA, Smith EO; Facial Nerve Disorders Committee. Facial Nerve Grading System 2.0. Otolaryngol Head Neck Surg. 2009 Apr;140(4):445-50.
  4. Gaudin RA, Robinson M, Banks CA, Baiungo J, Jowett N, Hadlock TA. Emerging vs Time-Tested Methods of Facial Grading Among Patients With Facial Paralysis. JAMA Facial Plast Surg. 2016 Jul 1;18(4):251-7.
  5. Fisch U. Maximal nerve excitability testing vs electroneuronography. Arch Otolaryngol. 1980;106:352-57.
  6. Gantz BJ, Gmuer AA, Holliday M, Fisch U. Electroneurographic evaluation of the facial nerve. Method and technical problems. Ann Otol Rhinol Laryngol. 1984 Jul-Aug;93(4 Pt 1):394-8.
  7. Byun H, Cho YS, Jang JY, Chung KW, Hwang S, Chung WH, Hong SH. Value of electroneurography as a prognostic indicator for recovery in acute severe inflammatory facial paralysis: a prospective study of Bell's palsy and Ramsay Hunt syndrome. Laryngoscope. 2013 Oct;123(10):2526-32.
     

Imaging

Learning Objectives 

To improve ability to differentiate between infectious and neoplastic processes on imaging.   Contrast enhancement may be seen in inflammatory conditions, while changes in nerve caliber are usually indicative of neoplasm.   

References 
  1. Swartz JD, Loevner LA, eds. Imaging of the Temporal Bone. 4th ed. New York: Thieme; 2007. 

Medical Therapies

Learning Objectives 

Understand the role of medical treatments for acute facial paralysis.

  • Large scale placebo controlled studies have evaluated the role of steroids in management of Bell palsy finding improved outcome with treatment.
  • The utility of antiviral medications in Bell palsy is inconclusive.  When used alone, they do not provide benefit. 
  • Outcomes are poorer in Ramsay Hunt (VZV mediated) syndrome than in Bell Palsy.  Steroids and antivirals are recommended for Ramsay Hunt syndrome, though definitive studies are lacking.  
  • Acute facial palsy due to Lyme disease may be best treated by antibiotics (doxycycline) alone. 
References 
  1. Peiterson E. The natural history of Bell's palsy. Am J Otol. 1982;4:107-11.
  2. Sullivan FM, Swan IR, Donnan PT, Morrison JM, Smith BH, McKinstry B, Davenport RJ, Vale LD, Clarkson JE, Hammersley V, Hayavi S, McAteer A, Stewart K, Daly F. Early treatment with prednisolone or acyclovir in Bell's palsy. N Engl J Med. 2007;357:1598-607.
  3. Engström M, Berg T, Stjernquist-Desatnik A, Axelsson S, Pitkäranta A, Hultcrantz M, Kanerva M, Hanner P, Jonsson L. Prednisolone and valacyclovir in Bell's palsy: a randomised, double-blind, placebo-controlled, multicentre trial. Lancet Neurol. 2008;7:993-1000.
  4. de Ru JA, van Benthem PP. Combination therapy is preferable for patients with Ramsay Hunt syndrome. Otol Neurotol. 2011 Jul;32(5):852-5.
  5. Jowett N, Gaudin RA, Banks CA, Hadlock TA. Steroid use in Lyme disease-associated facial palsy is associated with worse long-term outcomes. Laryngoscope. 2017 Jun;127(6):1451-1458.

Surgical Therapies

Learning Objectives 
  1. Discuss the timing of exploration and repair of traumatic facial paralysis.
    • Early exploration of extratemporal facial nerve injuries is encouraged since the distal nerve may be responsive to electrical stimulation for up to 72 hours.  
  2. Discuss the role of decompression in acute facial paralysis.
    • Facial nerve decompression must be performed within 2 weeks of onset for maximal benefit.  
References 
  1. Gantz BJ, Rubinstein JT, Gidley P, Woodworth GG. Surgical management of Bell's palsy. Laryngoscope. 1999;109:1177-88.
  2. Slattery WH, Azizzadeh B, eds. The Facial Nerve. New York: Thieme; 2014.
  3. Davis RE, Telischi FF. Traumatic facial nerve injuries: review of diagnosis and treatment. J Craniomaxillofac Trauma. 1995 Fall;1(3):30-41.

Rehabilitation

Learning Objectives 

Discuss methods of facial reanimation surgery to improve facial function and appearance.  

  • Functional priorities are effective eyelid closure and competence of the oral commissure.  
  • Mimetic movement requires adequate neural stimulus and sufficient muscle strength.  Long standing paralysis with resulting muscle fibrosis and atrophy will require free muscle grafting to restore movement. 
References 
  1. Garcia RM, Hadlock TA, Klebuc MJ, Simpson RL, Zenn MR, Marcus JR. Contemporary solutions for the treatment of facial nerve paralysis. Plast Reconstr Surg. 2015 Jun;135(6):1025e-1046e.
  2. Slattery WH, Azizzadeh B, eds. The Facial Nerve. New York: Thieme; 2014.
  3. May M, Schaitkin B, eds.  The Facial Nerve. New York: Thieme; 2000.

Review

Review Questions 
  1. How does the prognosis differ between Bell palsy and Ramsay Hunt Syndrome?
  2. When is surgical decompression of the facial nerve indicated?
  3. Discuss surgical options for congenital facial palsy. 
  4. What are the limitations of electroneuronography?
Resources 

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